Broadband hybrid-fiber/coax (HFC) networks provide a flexible, cost-effective platform for offering a wide range of telecommunications services to residences and businesses. One of these services, high-speed multimedia access, is a particularly attractive opportunity for HFC network operators. Some of the envisioned applications include Internet access, the ability to communicate with the office while working at home, voice and video telephony, interactive game playing, etc.
Although there is substantial near-term demand for basic high-speed data access over HFC networks, it is uncertain how interactive multimedia services will evolve over time. There is a strong trend towards the integration of data and non-data services within end-user applications. Highly compelling applications such as `audio plus data,` `voice plus data,` and `audio plus video plus data,` for personal computers and other devices, are all under development. Wide-area network transport infrastructures are migrating towards asynchronous transfer mode (ATM) as bandwidth and quality-of-service (QOS) issues become critical for supporting these applications.
HFC pure data systems installed in the near-term must be gracefully upgradeable to support these new integrated applications since it is unreasonable to require wholesale replacement of less flexible early generation equipment that has been optimized for a restricted class of data-centric applications, e.g., those requiring only transport of Ethernet frames or IP packets. Although it may be technically possible to add limited inefficient support for other traffic types to these early systems through "extensions," it is preferable to develop a flexible basic transport structure in place from the outset to provide for future evolution as warranted by the customer needs and business considerations. Such a transport system must be capable of transporting synchronous transfer mode (STM) information, such as voice and video telephony; variable length (VL) information, such as Internet Protocol (IP) or IEEE 802.3 frames; and asynchronous transfer mode (ATM) cells.